1. Field of the Invention
The invention relates to a method for the injection of aluminium wire or a similar product into molten steel, in which the wire is pulled from a coil by transport means which transport it to and into the steel bath. The invention also relates to an uncoiling apparatus for the uncoiling of aluminium wire or other wire product to be used in this method.
Although the invention is mainly intended to be applied to the injection of thick aluminium wire into molten steel in order to combine oxygen in the steel and is primarily described below in relation to this use, it is also applicable to the injection of wire of other sizes and of wire of similar sizes but of another composition. For instance, such wires can be used for the alloying of molten steel or for the addition of oxidizing elements. In that case, the wire may be of the hollow powder-filled type.
2. Description of the Prior Art
When combining free oxygen in molten steel, the so-called killing of the steel, it is of importance that an accurate as possible quantity of aluminium is mixed through the steel quickly and homogeneously, without in this process much of the aluminium oxiding prematurely. It is customary to supply aluminium wire of a diameter of 12 mm, at a speed of 8 to 9 m/sec, perpendicularly into the steel bath.
The standard manner in which aluminium wire is supplied is in parallel-wound coils with a weight of approximately 2,000 kg. A parallel-wound coil is one in which the wire windings are wound in layers next to and against each other. Until now, in practice, is has not appeared feasible to unwind the wire from such a coil at the required high speed, in a trouble-free manner and in an exact quantity. When unwinding a rolling coil, the total weight of the coil must first be accelerated and subsequently must be decelerated quickly, which in practice has led to big problems. It has also been suggested (see FIG. 3 of No. DE-B-2 554 860) to pull off such windings overhead, with the coil mounted on a mandrel and the wire passing through a guide above the mandrel, but in doing so it has appeared that the risk is high that several windings fly off the package simultaneously and hence get tangled, or also that several windings spontaneously get loose from the package and fall down and so get tangled.
In practice, therefore, the standard coils of 2,000 kg are recoiled to a bundle of windings, loosely wrapped around a mandrel, which can be pulled off reliably overhead (see FIGS. 1 and 2 of No. DE-B-2 554 680). Here no guide above the bundle is used. This method, however, also has disadvantages, for instance that the body or bundle so formed is very much more voluminous, so that only coils of 400 to 600 kg can be formed. This recoiling requires expensive recoiling installations, and the recoiling operation is time-consuming and requires much labour. Finally, it has appeared that the forming of such loosely wrapped coils leads requires a certain flexibility of the aluminium wire, which sets a top limit on the wire thickness of approximately 12 mm. The need exists for an injection method by which thicker aluminium wire can be injected, as in that case this injecting can be done at a correspondingly lower speed, which, in turn, requires a simpler drive system. Further, the use of thicker wire has the advantage that the risk of oxidation of aluminium at the molten bath is lower.
The invention, therefore, has the primary object to provide a method and an apparatus in which the recoiling of aluminium wire from the standard supplied parallel-wound coils of approximately 2,000 kg is no longer necessary and by which, if desired, thicker aluminium wire can be injected.
No. EP-A-70243 shows a method of uncoiling wire, e.g. for steel treatment, wherein no mandrel is used but the wire is pulled upwardly from the inside of the coil while the exterior of the coil is clamped. The wire is caused to slide on a roller which presses downwardly on the coil at one side to increase its curvature slightly and then passes through an eyelet above the coil. The use of the eyelet prevents the joining of two coils end-to-end.
While it is convenient to pull the wire from the inside of the clamped coil, the present invention has the further object to provide simpler and better control of the wire as it is pulled upwardly and to make possible the joining of two coils end-to-end.